Electric appliances and electronic appliances emit electromagnetic wave noises, and ambient electromagnetic wave noises intrude into them so that noises are contained in signals. To prevent the emission and intrusion of electromagnetic wave noises, electric appliances and electronic appliances have conventionally been shielded with metal sheets. It is also proposed to dispose electromagnetic-wave-absorbing films in electric appliances and electronic appliances to absorb electromagnetic wave noises.
For example, WO 2010/093027 A1 discloses a linear-scratched, thin metal film-plastic composite film with reduced anisotropy in electromagnetic wave absorbability, which comprises a plastic film and a single- or multi-layer, thin metal film formed on at least one surface of the plastic film, the thin metal film being provided with large numbers of substantially parallel, intermittent linear scratches with irregular widths and intervals in plural directions, and the thin metal film being made of aluminum, copper, nickel, or alloys thereof. WO 2010/093027 A1 describes that the linear-scratched, thin metal film-plastic composite film can be laminated with an electromagnetic wave reflector (a sheet, net or mesh of metal, a plastic film having a thin metal film, etc.) via a dielectric layer to obtain a composite electromagnetic wave absorber. This composite electromagnetic wave absorber has high absorbability to electromagnetic wave noise in a wide frequency, but does not have a function of exhibiting particularly large absorbability to electromagnetic wave noise at a particular frequency, and a function of shifting a frequency range in which the electromagnetic wave noise absorbability is maximized.
WO 2013/081043 A1 discloses an electromagnetic-wave-absorbing composite sheet comprising (a) a first electromagnetic-wave-absorbing film comprising a plastic film, and a single- or multi-layer, thin metal film formed on at least one surface of the plastic film, the thin metal film being made of at least one metal selected from the group consisting of aluminum, copper, silver, tin, nickel, cobalt, chromium and alloys thereof, and the thin metal film being provided with large numbers of substantially parallel, intermittent linear scratches with irregular widths and intervals in plural directions; and (b) a second electromagnetic-wave-absorbing film comprising magnetic particles or non-magnetic conductive particles dispersed in a resin or a rubber. This electromagnetic-wave-absorbing composite sheet has high absorbability to electromagnetic wave noise in a wide frequency range, but does not have a function of exhibiting particularly large absorbability to electromagnetic wave noise at a particular frequency, and a function of shifting a frequency range in which the electromagnetic wave noise absorbability is maximized.